Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. It is common to integrate multiple radios into a single communication device. For example, smartphones may have radios to support cellular communication, WiFi, GPS, and Bluetooth®, etc., with each radio operating on a different frequency band. A communication system may transmit (Tx) and receive (Rx) simultaneously on different frequency bands. Interference on an Rx signal of a victim receiver may be represented by leakage of Tx signals that are simultaneously transmitted by one or more aggressor transmitters of the same communication system, thus referred to as self-jamming interference. The Tx signals may leak to the Rx path through the finite isolation between the Tx and Rx paths of the communication system. For example, in a system containing a 3GPP Long Term Evolution (LTE) radio and a WiFi radio, non-linearities present in the transmitter chain, such as in an up-converter or a power amplifier (PA) of the LTE transmitter, may generate spectral re-growth of the LTE Tx signal that falls in the Rx frequency band of the WiFi receiver as a leakage signal. Even when the Tx leakage signal occupies a nominally different frequency band from the WiFi Rx signal, the Tx leakage signal may cause co-channel interference on the intended WiFi Rx signal due to non-linearities in the Rx chain. For example, non-linear behavior in the radio frequency (RF) down conversion components, e.g., non-linear excitation of low noise amplifiers (LNA), mixers, switches, filters, data converters, etc., operating on the Tx leakage signal may generate interference in the Rx frequency band. The effects of the self-jamming interference due to the non-linearities of the Tx or the Rx chains are degradation in the performance of the communication systems or even a reduction of coverage area.
In a communication system affected by self-jamming interference, the Tx waveforms that generate the interference may be known. Hence, the communication system may reconstruct the interference component of the Rx signal at the victim Rx chain via an adaptive non-linear interference cancellation (NLIC) scheme. For example, an NLIC module may generate, based on the known baseband Tx signal, an estimate of the interference signal component of the baseband Rx signal attributable to the Tx/Rx non-linearities. The Rx chain may remove the estimated interference signal component from the baseband Rx signal to cancel or to mitigate the self-jamming interference.
Often a receiver victimized by self-jamming interference may have multiple Rx chains each of which has an Rx antenna and an Rx front-end. For example, multiple-input multiple-output (MIMO) receivers or other receivers with antenna diversity have multiple Rx antennas. Each of the antennas may receive self-jamming interference from the same Tx interference signal source. For example, multiple antennas of a MIMO WiFi receiver may receive interference signals from an LTE transmitter co-located in the system. However, the characteristics of the self-jamming interference received by each of the Rx chains may be different due to differences in signal path, differences in antenna isolation from the Tx interference source to the each victim Rx antenna, and/or due to differences in device characteristics of the multiple Rx front-ends. The receiver may implement an NLIC module for each Rx chain to independently estimate the interference signal received by each Rx chain for interference cancellation. However, estimating the interference signals for the multiple Rx chains using independent NLIC modules increases complexity, cost, size, and power of the receiver. In addition, an Rx chain of the Rx antenna having a low level of interference may not accurately estimate the interference signal in the present of noise, thus negatively impacting receiver performance. The increased complexity, cost, and degraded performance may limit the implementation of the NLIC scheme in receivers with multiple Rx antennas or may restrict the ability of the receivers to scale up the number of antennas to increase throughput and performance.